A multi-speed transmission with nine forward gears and one reverse gear is known from DE 10 2008 000 429 A1. The multi-speed transmission includes four planetary gear sets, eight rotatable shafts and six shifting elements. The first and second planetary gear sets form a shiftable upstream gear set, while the third and fourth planetary gear sets constitute a so-called “main gear set.” The carriers of the first and second planetary gear sets are coupled with each other by one of the rotatable shafts, which is connected to an element of the main gear set. The ring gear of the first planetary gear set is coupled with the sun gear of the second planetary gear set by an additional shaft of the rotatable shafts, which is detachably connectable to a drive shaft by a clutch.
The sun gear of the first planetary gear set is attachable by an additional shaft of the rotatable shafts through a brake to a housing of the multi-speed transmission and is connectable to the drive shaft by a clutch. The ring gear of the second planetary gear set is attachable to the housing by a shaft through a brake. In turn, an additional shaft of the rotatable shafts is connected to at least one element of the main gear set and is attachable to a housing by the brake. An additional shaft of the rotatable shafts is connected to an additional element of the main gear set and is connectable to the drive shaft by a shifting element designed as a clutch, while an output shaft is connected to at least one additional element of the main gear set. At least two of the shifting elements of the multi-speed transmission are formed as positive-locking shifting elements, which are switched off only during upshifts.
In order to save fuel, in addition to so-called “start-stop systems,” vehicles are increasingly equipped with so-called “coasting functions,” by which, during travel, an internal combustion engine is switched off and is decoupled from the rest of the drive train. During such an activated coasting mode function, the existing kinetic energy of a motor vehicle is used for locomotion, instead of being lost in the form of towing capacity. In hybrid vehicles, this coasting mode function is already widely used, but the coasting function is also increasingly being used in conventional vehicles with internal combustion engine. In contrast to start-stop systems, in which the engine is only switched off during the standstill of a vehicle, with an activated coasting mode function, the shutdown of an engine designed as an internal combustion engine takes place already during the rolling operating state of a vehicle.